Identification of the avian tracheal trematode Typhlocoelum cucumerinum (Trematoda: Cyclocoelidae) in a host-parasite-environment system: diagnosis, life cycle and molecular phylogeny.

Typhlocoelum cucumerinum is a tracheal parasite of birds widely distributed across the globe. Nevertheless, aspects of the biology of this cyclocoelid are still poorly understood. Herein, we report the finding of T. cucumerinum in definitive and intermediate hosts from an urban waterbody of Brazil. The parasite was initially detected during the necropsy of domestic Muscovy ducks (Cairina moschata) found dead in the locality. Coproparasitological tests in live animals revealed that 12/47 (25.53%) Muscovy ducks and 2/8 (25%) mallards (Anas platyrhynchos platyrhynchos) were infected with T. cucumerinum. Moreover, rediae and metacercariae morphologically similar to T. cucumerinum were found in 3/248 (1.33%) Biomphalaria straminea collected in the same waterbody frequented by the birds. The conspecificity between the adult and the larval stages was confirmed molecularly (100% similarity in Cox-1). Moreover, the phylogenetic position of T. cucumerinum was determined for the first time based on partial fragments of the 28S, Cox-1 and Nad-1 genes. The species grouped with other members of the subfamily Typhlocoelinae with sequences available, but the data obtained do not support the distinctiveness of the genera Typhlocoelum and Tracheophilus. Further studies involving a broader range of species can result in taxonomic rearrangements in Typhlocoelinae.

Polyostotic osteosarcoma associated with avian leukosis virus infection in a captive bare-faced curassow (Crax fasciolata).

BACKGROUND: Osteosarcoma is a malignant mesenchymal bone tumor. Although it is a common tumor in the appendicular skeleton of dogs and cats, it is rarely reported in birds. Retroviruses are usually associated with solid tumor development in different avian species. CASE PRESENTATION: This report aims to describe a case of osteosarcoma associated with the avian leukosis virus in a captive bare-faced curassow (Crax fasciolata). A captive adult female bare-faced curassow presented with lameness, hyporexia, and a non-ulcerative and firm tumor in the right femur. The bird was euthanized due to the poor prognosis. Histopathology revealed an infiltrative mesenchymal neoplasm consisting of spindle cells with moderate cell pleomorphism, organized in bundles and interspersed by marked deposition of the osteoid matrix, which was compatible with osteosarcoma affecting both femur and tibiotarsus, with renal metastasis. Immunohistochemistry of the primary and metastatic tumor demonstrated vimentin expression by neoplastic cells. Samples of the neoplasm, bone marrow, and spleen were processed for PCR, which enabled the demonstration of proviral avian leukosis virus (ALV) DNA. CONCLUSIONS: To the best of our knowledge, this is the first report of an osteosarcoma in a bare-faced curassow with an unusual polyostotic manifestation and associated with ALV infection.

Avian Pox in Native Captive Psittacines, Brazil, 2015.

To investigate an outbreak of avian pox in psittacines in a conservation facility, we examined 94 birds of 10 psittacine species, including sick and healthy birds. We found psittacine pox virus in 23 of 27 sick birds and 4 of 67 healthy birds. Further characterization is needed for these isolates.

Antitoxin therapy of natural avian botulism outbreaks occurred in Brazil.

Botulism commonly affects water birds and it has recently been observed to be emerging in poultry production. In the present work, outbreaks of botulism in wild native species, such as the black-fronted Piping-guan (Aburria jacutinga), wild duck (Cairina moschata) and its crosses with mallard (Anas platyrhynchos), and domestic chickens (Gallus gallus domesticus) are described. Following treatments with a commercial botulism antitoxin CD, 28 (96.5%) out of 29 animals fully recovered after 24-72 h. The antitoxin therapy was shown to be a useful option for the treatment of affected birds, including those that were severely affected.

Interactions of Plasmodium juxtanucleare and chicken anaemia virus: establishing a model.

The pathogens Plasmodium juxtanucleare and chicken anaemia virus (CAV) are easily transmitted and potentially harmful to chickens. In this study, we established an experimental model to investigate the effects of avian malaria caused by P. juxtanucleare in white leghorn specific-pathogen-free (SPF) chicks previously immunosuppressed with CAV. Parasitaemia, haematological variables and clinical and pathological parameters were determined in four different experimental groups: chicks coinfected by CAV and P. juxtanucleare strain (Coinfected group), chicks exclusively infected by CAV (CAV group) or P. juxtanucleare (Malaria group) and uninfected chicks (Control group). Our data demonstrated that P. juxtanucleare parasitaemia was significantly higher in the Coinfected group. Furthermore, haematological parameters, including the RBC, haematocrit and haemoglobin concentration were significantly reduced in coinfected chicks. In agreement with the changes observed in haematological features, the mortality among coinfected chicks was higher compared with animals with single infections. Clinical analysis indicated moderate changes related to different organs size (bursa of Fabricius, heart and liver) in coinfected birds. The experimental coinfection of SPF chickens with P. juxtanucleare and CAV may represent a research tool for the study of avian malaria after CAV immunosuppression, enabling measurement of the impacts caused by different pathogens during malarial infection.

Acute infection with Platynosomum illiciens (Trematoda: Dicrocoeliidae) as a clinically relevant and potentially fatal disease in Falco sparverius (Aves: Falconidae) in Brazil.

Platynosomum illiciens is a dicrocoeliid trematode from the biliary tract of warm-blooded vertebrates (felines, primates, marsupials, and birds) reported in different parts of the world. Although the veterinary relevance of platynosomosis in mammals, especially in domestic felines, has been increasingly evidenced in the scientific literature, studies involving avian disease caused by P. illiciens are comparatively scarce. In the present study, a female specimen of the American kestrel, Falco sparverius L., found dead, in November 2019, in Brazil, was necropsied. Parietal biliary effusion in the celomatic cavity was observed, suggesting biliary transudation and gallbladder stasis, which possibily preceded the distension and rupture of gallbladder noted during necropsy. In the microscopic analysis of the bile content, small trematodes were found and characterized as immature stages of Platynosomum after the morphological study. Partial sequences of the cox-1 gene enabled the identification of P. illiciens, with 100% similarity with previously sequenced sympatric isolates from mammals. The finding of immature specimens in a ruptured gallbladder strongly suggests a role for the parasite in biliary flow dysfunction, indicating acute platynosomosis as a clinically relevant and potentially fatal condition that has not yet been discussed.

Fatal coccidiosis by Isospora icterus (Upton & Whitaker, 2000) in captive Campo Troupial (Icterus jamacaii) in Brazil.

An outbreak of coccidiosis by Isospora icterus (I. icterus, Upton & Whitaker, 2000) in captive Campo Troupial (Icterus jamacaii) (Gmelin, 1788) at the Wild Animals Triage Center (IBAMA, Belo Horizonte, Brazil) is described. Clinical history and the necropsy findings documented diarrhea with diffuse necrotic enteritis. Sporulated oocysts (n = 100) had a bilayered wall, were subspherical, and measured 30.1 (27.5-32.5) microm in length and 28.5 (26.2-30.0) microm in width. A polar body but no micropyle was present and the length/width ratio was 1.1 (1.00-1.2). Each oocyst contained two ellipsoidal sporocysts measuring 17.6 (15.0-20.0) microm in length and 12.9 (12.5-15.0) microm in width, with a length/width ratio of 1.4 (1.2-1.5), and with Stieda and sub-Stieda bodies. Each sporocyst contained four sporozoites with granular sporocyst residuum. Oocysts were compatible with those from I. icterus, previously described in Campo Troupial.

NEW RECORDS OF NEMATODES IN THE YELLOW-BILLED CUCKOO COCCYZUS AMERICANUS (CUCULIFORMES: CUCULIDAE) BASED ON A MIGRANT SPECIMEN FOUND IN BRAZIL.

The yellow-billed cuckoo, Coccyzus americanus, is a threatened passerine bird native to North America that migrates to overwinter in South America. Although migratory birds have drawn broad attention, given their assumed role in the long-distance dispersal of parasites, studies on the helminth fauna of this cuculid are scarce. In the present study, nematodes found in the gastrointestinal tract of a specimen of C. americanus found in Belo Horizonte, State of Minas Gerais, southeastern Brazil, were characterized morphologically. Five species of gastrointestinal nematodes belonging to 4 families were identified: Synhimantus (Dispharynx) nasuta (Rudolphi, 1819) and Synhimantus (Dispharynx) resticulaCanavan, 1929 (Acuariidae), Microtetrameres sp. (Tetrameridae), and Cyrnea piayaeSandground, 1929 (Habronematidae) and Subulura halli Barreto, 1918 (Subuluridae). Except for Microtetrameres sp., all other nematodes are reported in this host for the first time. Although it is difficult to accurately determine the geographical origin of infections, it is important to note that Sy. (D.) resticula and Su. halli are reported for the first time in Brazil. Additionally, the absence of the former species infecting hosts where the widespread and generalist Sy. (D.) nasuta was found may indicate that Sy. (D.) resticula have either been overlooked in previous studies or that this nematode is rare indeed. Finally, the geographical distribution of Su. halli is greatly expanded and now includes the Americas. Aspects related to the dispersion of these parasites, both in migrating and native hosts, are briefly discussed.

Yeast mannans inhibit binding and phagocytosis of zymosan by mouse peritoneal macrophages.

We have examined the effects of various mannans, glycoproteins, oligosaccharides, monosaccharides, and sugar phosphates on the binding and phagocytosis of yeast cell walls (zymosan) by mouse peritoneal macrophages. A phosphonomannan (PO(4):mannose ratio = 1:8:6) from kloeckera brevis was the most potent inhibitor tested; it inhibited binding and phagocytosis by 50 percent at concentrations of approximately 3-5 mug/ml and 10 mug/ml, respectively. Removal of the phosphate from this mannan by mild acid and alkaline phosphatase treatment did not appreciably reduce its capacity to inhibit zymosan phagocytosis. The mannan from saccharomyces cerevisiae mutant LB301 inhibits phagocytosis by 50 percent at 0.3 mg/ml, and a neutral exocellular glucomannan from pichia pinus inhibited phagocytosis by 50 percent at 1 mg/ml. Cell wall mannans from wild type S. cervisiae X2180, its mnn2 mutant which contains mannan with predominantly 1(arrow)6- linked mannose residues, yeast exocellular mannans and O-phosphonomannans were less efficient inhibitors requiring concentrations of 1-5 mg/ml to achieve 50 percent reduction in phagocytosis. Horseradish peroxidase, which contains high-mannose type oligosaccharides, was also inhibitory. Mannan is a specific inhibitor of zymosan binding and phagocytosis. The binding and ingestion of zymosan but not of IgG- or complement-coated erythrocytes can be obliterated by plating macrophages on substrates coated with poly-L-lysin (PLL)-mannan. Zymosan uptake was completely abolished by trypsin treatment of the macrophages and reduced by 50-60 percent in the presence of 10 mM EGTA. Pretreatment of the macrophages with chloroquine inhibited zymosan binding and ingestion. These results support the proposal that the macrophage mannose/N-acetylglucosamine receptor (P. Stahl, J.S. Rodman, M.J. Miller, and P.H. Schlesinger, 1978, Proc. Natl. Acad. Sci. U.S.A. 75:1399-1403, mediates the phagocytosis of zymosan particles.

Delay of disease development in transgenic plants that express the tobacco mosaic virus coat protein gene.

A chimeric gene containing a cloned cDNA of the coat protein (CP) gene of tobacco mosaic virus (TMV) was introduced into tobacco cells on a Ti plasmid of Agrobacterium tumefaciens from which tumor inducing genes had been removed. Plants regenerated from transformed cells expressed TMV mRNA and CP as a nuclear trait. Seedlings from self-fertilized transgenic plants were inoculated with TMV and observed for development of disease symptoms. The seedlings that expressed the CP gene were delayed in symptom development and 10 to 60 percent of the transgenic plants failed to develop symptoms for the duration of the experiments. Increasing the concentration of TMV in the inoculum shortened the delay in appearance of symptoms. The results of these experiments indicate that plants can be genetically transformed for resistance to virus disease development.

Experimental avian philophthalmosis: Evaluation of diagnosis and treatment of chickens infected with Philophthalmus gralli (Trematoda: Philophthalmidae).

The trematodes of the genus Philophthalmus are eye flukes that cause damage to ocular structures of animals and humans. Despite the increasing number of cases reported in birds, studies related to the diagnosis of subclinical philophthalmosis are lacking, and there are no effective therapeutic regimens available. In the present study, we evaluated the diagnosis and treatment of philophthalmosis in specific pathogen-free chickens (Gallus gallus domesticus) experimentally infected with Philophthalmus gralli. Four chickens were inoculated with metacercariae of P. gralli (20 per eye) obtained from cercariae emerged from naturally infected Melanoides tuberculata. From 90 days post-infection, the chickens were subjected to direct ophthalmic examination (DOE) and conjunctival sac lavage (CSL). The latter technique consisted of lavage of each eye with 200 µL sterile saline solution and subsequent microscopical examination of the collected fluid for the presence of eggs of P. gralli. The anthelminthic treatment protocols included praziquantel (PZQ) at 10, 50, or 100 mg/kg (single dose given intramuscularly), or fenbendazole (FBZ) at 50 mg/kg (three doses at 24 h-intervals given per os). The treatment protocols were performed at 14 day-intervals between each dosage of PZQ. Chickens developed a minimum of one to more than five adult P. gralli per eye, except for one chicken that had a single eye with one parasite. No ocular clinical signs or changes in behavior were noted in any chickens. DOE and CSL were considered techniques with similar sensitivity for the diagnosis of avian philophthalmosis. The data suggested that PZQ and FBZ, at the dosages and schedules employed, are not effective for the complete elimination of P. gralli. CSL is proposed as a complementary technique for the diagnosis and monitoring of philophthalmosis post-treatment, especially in subclinical cases. The evaluation of new protocols, routes of administration, and anthelmintic drugs are needed for successful pharmacological treatment of philophthalmosis.

Haemoproteus paraortalidum n. sp. in captive Black-fronted Piping-guans Aburria jacutinga (Galliformes, Cracidae): High prevalence in a population reintroduced into the wild.

Haemosporidian parasites of the genus Haemoproteus are widespread and can cause disease and even mortality in birds under natural and captive conditions. The Black-fronted Piping-guan (Aburria jacutinga) is an endangered Neotropical bird of the Cracidae (Galliformes) going through a reintroduction program to avoid extinction. We used microscopic examination and partial cytochrome b DNA sequencing to describe a new Haemoproteus species infecting Black-fronted Piping-guans bred and raised in captivity that were reintroduced into the Atlantic rainforest. Haemoproteus (Parahaemoproteus) paraortalidum n. sp. was detected in the blood of 19 out of 29 examined birds. The new species is distinguished from other haemoproteids due to the shape of gametocytes, which have pointed ends in young stages, and due to the presence of vacuole-like unstained spaces in macrogametocytes and numerous volutin granules both in macro- and microgametocytes. Illustrations of the new species are provided. Phylogenetic inference positioned this parasite in the Parahaemoproteus subgenus clade together with the other two Haemoproteus genetic lineages detected in cracids up to date. We discuss possible implications of the reintroduction of birds infected with haemosporidian parasites into the wild. Treatment of Haemoproteus infections remains insufficiently studied, but should be considered for infected birds before reintroduction to improve host reproductive and survival rates after release.

First Report of the Perfect Stage of Powdery Mildew of Sugar Beet in North Dakota Caused by Erysiphe polygoni.

Powdery mildew caused by Erysiphe polygoni was widespread on sugar beet (Beta vulgaris) in North Dakota during 2006. This disease is generally not prevalent in the state because of the application of fungicides, which also have efficacy against powdery mildew, for control of Cercospora leaf spot caused by Cercospora beticola. Because Cercospora leaf spot pressure was low in 2006, fewer fungicide applications were made in the state, thus allowing for more observations of powdery mildew. Leaf samples from four fields near Amenia, Minto, Prosper, and St. Thomas, ND were collected in mid-September to look for the perfect stage of E. polygoni, since this has recently been observed in Idaho, Colorado, Montana, and Nebraska (1-3). Only the leaves collected from the field near Amenia had visible immature (yellow and brown) globose ascomata; ascomata were not observed on the leaves collected in the other fields. Additional leaves were collected from the field near Amenia in early October; these leaves had immature and mature (black) globose ascomata that were 70 to 105 µm in diameter. Mature ascomata contained ovoid to elliptic asci with one to four hyaline-to-golden pigmented ascospores (20 to 25 × 12 to 20 µm). The color, shape, and size of ascomata, asci, and ascospores were similar to previously reported observations (1-4). The prevalence of the perfect stage in North Dakota is unknown, since no statewide surveys were conducted. To our knowledge, this is the first report of the perfect stage of E. polygoni on sugar beet in North Dakota. The occurrence of the perfect stage could lead to a means for overwintering in this area. Because of the means for genetic recombination, the risk of fungicide resistance and the development of races may increase. References: (1) J. J. Gallian and L. E. Hanson. Plant Dis. 87:200, 2003. (2) R. M. Harveson. Plant Dis. 88:1049, 2004. (3) B. Jacobsen et al. Plant Dis. 89:1362, 2005. (4) E. G. Ruppel. Powdery mildew. Pages 13-15 in: Compendium of Beet Diseases and Insects. E. D. Whitney and J. E. Duffus, eds. The American Phytopathological Society. St. Paul, MN, 1986.

Molecular analysis of Brazilian infectious bronchitis field isolates by reverse transcription-polymerase chain reaction, restriction fragment length polymorphism, and partial sequencing of the N gene.

Molecular analysis of 15 Brazilian infectious bronchitis virus (IBV) isolates, obtained from clinical outbreaks of the disease in chickens (broilers or layers) in the state of Minas Gerais (Brazil) between 1972 and 1989, is reported. Using the N protein gene as target, IBVs were analyzed by reverse transcription-polymerase chain reaction/restriction fragment length polymorphism (RT-PCR/RFLP) with the restriction enzymes AvaII, HphI, Sau96I, and Tsp509I and cDNA sequencing. Results obtained from those isolates were compared to 19 sequences available in GenBank. N gene RFLP profiles, cDNA sequences, and predicted amino acid composition were used for the construction of dendrograms. Brazilian isolates were grouped into one distinct group. Identity of predicted N protein amino acid composition varied from 45% (between isolates G and 208) up to 99% (PM 1 and PM2), and, when compared to the other IBVs, the amino acid identity was from 42% (Q3/88 and G) up to 97% (D41 and PM1). The great genetic diversity was shown to occur before the official use of vaccination in Brazil and has remained thereafter.

Distribution of Lyb-4.1 and other membrane antigens on murine lymphoid tumors.

The distribution of membrane antigens on 6 DBA/2-derived tumors (L1210, L5178Y, P815, ABLS 11, ABLS 12, and ABLS 13) was studied by direct cytotoxicity and quantitative absorption assays. Lyb-4.1 antigen was found solely on the L1210 tumor. Iad antigens were absent from all tumors, and H-2Kd and H-2Dd antigens were present on all tumors. Immunoglobulin was adsorbed to the ascites tumors and lost after 3 days or more in tissue culture. These studies were performed to characterize the distribution of DBA/2 membrane antigens on DBA/2-derived tumors as a base line for functional and chemical studies with these tumors and with their solubilized proteins.

Evaluation of actions of the official veterinary service to mitigate outbreaks of infectious laryngotracheitis and improve biosecurity on laying hen farms / Avaliação de ações do serviço veterinário oficial para bloqueio de foco de laringotraqueite infecciosa e melhoria da biosseguridade em granjas de postura

Infectious laryngotracheitis (ILT), caused by an Alphaherpesvirus (Gallid herpesvirus-1; GaHV-1), has been noticed in the region of the Terras Altas da Mantiqueira, Minas Gerais. From 2010 to 2018, the "Serviço Veterinário Oficial" (SVO) of the "Instituto Mineiro Agropecuário" (IMA), implemented measures to prevent spread of the virus to other regions and control the disease in the area. Due to the close proximity and consequent epidemiological link among farms, the region was considered a unique epidemiological unit. To check the efficiency of the ILT control measures, we carried out: (1) a seroepidemiological survey, (2) questionnaires for evaluating biosecurity measures; and (3) an evaluation of the influence of farm population density on the occurrence of ILT. In 2016, 2017, and 2018, ILT was investigated using epidemiological and clinicopathological methods, along with GaHV-1 molecular detection. Serological survey was carried out on 24 farms in the quarantined region and on 13 farms from other regions of the state. In 2010 and 2018, questionnaires were applied to collect data and determine indicators of biosecurity practices in all farms of the quarantined area. The differences were then assessed (Wilcoxon's p<0.05). The results indicated positive serology throughout the region, although only on four farms (16.6%) the chickens have clinical signs, macroscopic and histological lesions of ILT. The prevalence of viral infection increased from 2016 (27%) to 2017 (50%) and was higher in farms with a high stock density (p=0.033). No disease, virus or antibodies were detected in the farms outside of the quarantined area. Although the biosecurity indicators had improved on all farms in the quarantined area (p<0.05), the virus was active and circulating in the region. The contingency measures have contained the outbreak, but biosecurity practices are paramount in the control of new outbreaks. Official control will be maintained in the region, including surveillance of new cases and biosecurity procedures to mitigate the risk of the virus reaching other regions.(AU)

Laringotraqueíte infecciosa (LTI), causada por um alfaherpesvírus (herpesvírus Gallid-1; GaHV-1), foi observada na região das Terras Altas da Mantiqueira, Minas Gerais. De 2010 a 2018, o Serviço Veterinário Oficial (SVO) do Instituto Mineiro Agropecuário (IMA) implementou medidas para impedir a disseminação do vírus para outras regiões do estado e controlar a doença na região interditada. Devido à proximidade e consequente vínculo epidemiológico entre as granjas, a região foi considerada uma unidade epidemiológica única. Para verificar a eficiência das medidas de controle de LTI, foram realizados: (1) pesquisa soroepidemiológica, (2) questionários para avaliar medidas de biosseguridade; e (3) avaliação da influência da densidade populacional da granja na ocorrência de LTI. Em 2016, 2017 e 2018, a LTI foi investigada usando métodos epidemiológicos e clínico-patológicos, com a detecção molecular de GaHV-1. O levantamento sorológico foi realizado em 24 granjas da região interditada e em 13 granjas de outras regiões do estado. Em 2010 e 2018, foram aplicados questionários para coletar dados e determinar indicadores de medidas de biosseguridade em todas as granjas da área interditada. As diferenças foram avaliadas (p<0,05 de Wilcoxon). Os resultados indicaram sorologia positiva em toda a região, embora apenas em quatro granjas (16,6%) as galinhas apresentaram sinais clínicos, lesões macroscópicas e histológicas da LTI. A prevalência de infecção viral aumentou de 2016 (27%) para 2017 (50%) e foi maior em fazendas com alta densidade de alojamento (p=0,033). Presença da doença, vírus ou anticorpos foram detectados nas granjas fora da área interditada. Embora os indicadores de biosseguridade tenham melhorado em todas as fazendas da área interditada (p<0,05), o vírus está ativo e circulava na região. As medidas de contingência contiveram o surto, mas as práticas de biosseguridade são fundamentais para o controle de novos surtos. O controle oficial será mantido na região, incluindo a vigilância de novos casos e procedimentos de biosseguridade para mitigar o risco de transmissão do vírus para outras regiões.(AU)

Evaluation of actions of the official veterinary service to mitigate outbreaks of infectious laryngotracheitis and improve biosecurity on laying hen farms

ABSTRACT: Infectious laryngotracheitis (ILT), caused by an Alphaherpesvirus (Gallid herpesvirus-1; GaHV-1), has been noticed in the region of the Terras Altas da Mantiqueira, Minas Gerais. From 2010 to 2018, the Serviço Veterinário Oficial (SVO) of the Instituto Mineiro Agropecuário (IMA), implemented measures to prevent spread of the virus to other regions and control the disease in the area. Due to the close proximity and consequent epidemiological link among farms, the region was considered a unique epidemiological unit. To check the efficiency of the ILT control measures, we carried out: (1) a seroepidemiological survey, (2) questionnaires for evaluating biosecurity measures; and (3) an evaluation of the influence of farm population density on the occurrence of ILT. In 2016, 2017, and 2018, ILT was investigated using epidemiological and clinicopathological methods, along with GaHV-1 molecular detection. Serological survey was carried out on 24 farms in the quarantined region and on 13 farms from other regions of the state. In 2010 and 2018, questionnaires were applied to collect data and determine indicators of biosecurity practices in all farms of the quarantined area. The differences were then assessed (Wilcoxons p 0.05). The results indicated positive serology throughout the region, although only on four farms (16.6%) the chickens have clinical signs, macroscopic and histological lesions of ILT. The prevalence of viral infection increased from 2016 (27%) to 2017 (50%) and was higher in farms with a high stock density (p=0.033). No disease, virus or antibodies were detected in the farms outside of the quarantined area. Although the biosecurity indicators had improved on all farms in the quarantined area (p 0.05), the virus was active and circulating in the region. The contingency measures have contained the outbreak, but biosecurity practices are paramount in the control of new outbreaks. Official control will be maintained in the region, including surveillance of new cases and biosecurity procedures to mitigate the risk of the virus reaching other regions.

RESUMO: Laringotraqueíte infecciosa (LTI), causada por um alfaherpesvírus (herpesvírus Gallid-1; GaHV-1), foi observada na região das Terras Altas da Mantiqueira, Minas Gerais. De 2010 a 2018, o Serviço Veterinário Oficial (SVO) do Instituto Mineiro Agropecuário (IMA) implementou medidas para impedir a disseminação do vírus para outras regiões do estado e controlar a doença na região interditada. Devido à proximidade e consequente vínculo epidemiológico entre as granjas, a região foi considerada uma unidade epidemiológica única. Para verificar a eficiência das medidas de controle de LTI, foram realizados: (1) pesquisa soroepidemiológica, (2) questionários para avaliar medidas de biosseguridade; e (3) avaliação da influência da densidade populacional da granja na ocorrência de LTI. Em 2016, 2017 e 2018, a LTI foi investigada usando métodos epidemiológicos e clínico-patológicos, com a detecção molecular de GaHV-1. O levantamento sorológico foi realizado em 24 granjas da região interditada e em 13 granjas de outras regiões do estado. Em 2010 e 2018, foram aplicados questionários para coletar dados e determinar indicadores de medidas de biosseguridade em todas as granjas da área interditada. As diferenças foram avaliadas (p 0,05 de Wilcoxon). Os resultados indicaram sorologia positiva em toda a região, embora apenas em quatro granjas (16,6%) as galinhas apresentaram sinais clínicos, lesões macroscópicas e histológicas da LTI. A prevalência de infecção viral aumentou de 2016 (27%) para 2017 (50%) e foi maior em fazendas com alta densidade de alojamento (p=0,033). Presença da doença, vírus ou anticorpos foram detectados nas granjas fora da área interditada. Embora os indicadores de biosseguridade tenham melhorado em todas as fazendas da área interditada (p 0,05), o vírus está ativo e circulava na região. As medidas de contingência contiveram o surto, mas as práticas de biosseguridade são fundamentais para o controle de novos surtos. O controle oficial será mantido na região, incluindo a vigilância de novos casos e procedimentos de biosseguridade para mitigar o risco de transmissão do vírus para outras regiões.

Response of Tall Fescue Genotypes to a New Strain of Brome mosaic virus.

Brome mosaic virus (BMV) infects many different species within the Poaceae family. A new strain of BMV, named F-BMV, was identified in a tall fescue (Festuca arundinacea Schreb.) plant. Here, we report the identification and characterization of tall fescue plants resistant to F-BMV, and the effects of F-BMV infection on their growth and development. Susceptible plants infected with F-BMV produced 40% fewer tillers and 42% less dry matter compared with virus-resistant plants in a greenhouse study. In the field, susceptible plants infected with F-BMV produced 25% fewer tillers, 36% less dry matter, 10% less plant height, and 40% lower seed yield compared with virus-resistant plants. In a field evaluation of a tall fescue mapping population, the virus symptom scores were negatively correlated with production of dry matter (r = -0.55), plant height (r = -0.55), and seed yield (r = -0.33). Thus, F-BMV has the potential to cause significant economic damage to susceptible tall fescue plants. These results indicate that the virus can present a serious challenge for long-term maintenance of valuable plant materials. A survey of tall fescue plants from Arkansas, Oklahoma, and Oregon indicated that the prevalence F-BMV in the field was very low.

Potato spindle tuber viroid as inducer of RNA silencing in infected tomato.

Potato spindle tuber viroid (PSTVd), an RNA plant pathogen encoding no known proteins, induces systemic symptoms on tomato plants. We report detection of small RNAs of approximately 25 nucleotides with sequence specificity to PSTVd in infected plants: an indication of the presence of RNA silencing. RNA silencing, however, did not appear to be responsible for the differing symptoms induced by a mild and a severe strain of PSTVd. The unique structural and biological features of viroids make them attractive experimental tools to investigate mechanisms of RNA silencing and pathogen counterdefense.

Characterization of the masked strain of tobacco mosaic virus: identification of the region responsible for symptom attenuation by analysis of an infectious cDNA clone.

A strain of tobacco mosaic virus (TMV) that produces mild (attenuated) symptoms on tobacco plants has been molecularly cloned to identify the region of the genome responsible for symptom attenuation. A full-length cDNA clone whose transcripts produce the parental disease phenotype on both systemic and hypersensitive host plants has been constructed. This infectious clone was sequenced, and 55 base changes relative to the published sequence of common TMV (strain U1) were identified. These changes resulted in 12 amino acid alterations in the open reading frames encoding the 126/183-kDa and 30-kDa movement proteins; two of these changes were determined not to be responsible for the attenuated phenotype. Exchange of restriction fragments between the infectious mild strain cDNA and an infectious U1 strain cDNA indicated that the determinants involved in symptom attenuation reside in the open reading frame encoding the 126/183-kDa proteins of TMV; these proteins are involved in viral replication.